Neutral Density (ND) filters are designed to uniformly reduce light intensity without altering the spectral distribution of the incident beam.
Shape Optics supplies a comprehensive range of reflective metallic ND filters, absorptive glass ND filters, and hybrid ND designs, delivering spectrally even attenuation—particularly across the visible (VIS) spectrum—with coverage extending from UV to IR.
Reflective ND filters utilize vacuum-deposited metallic alloys (such as chromel) to attenuate light primarily through reflection with partial absorption. This approach significantly reduces thermal loading on downstream optics, making them ideal for high-power illumination and laser systems.
Absorptive ND filters, by contrast, rely on light-absorbing optical glass to achieve stable, wavelength-independent attenuation. These filters are well suited for broadband imaging, photometry, and laboratory instrumentation requiring compact and mechanically robust solutions.
Key Features
- Spectrally Neutral Performance – Preserves relative spectral balance, especially in the VIS range
- Broadband Coverage – Selectable attenuation from 250–2500 nm (UV–VIS–IR)
- Wide Optical Density Range – OD 0.04 to 4.0, stackable for higher attenuation
- Thermal-Friendly Designs – Reflective ND options minimize heat absorption
- Flexible Constructions – Exposed metallic, protected laminated, or absorptive glass designs
Optical Density (OD) Definition
OD = −log₁₀(T), where T is transmission.
Example:
OD 0.8 → 16% transmission
Optical densities add linearly when stacked:
OD 0.5 + OD 0.3 = OD 0.8
A standard six-filter set (OD 0.1, 0.3, 0.5, 1.0, 2.0, 3.0) enables graduated attenuation from OD 0.1 up to OD 6.9.
General Specifications
Optical Performance
OD Tolerance @ 550 nm
OD < 1.0: ±0.05
OD 1.0–3.0: ±0.10
OD > 3.0: ±0.20
Neutrality (400–700 nm): Variation ≤ 10% of OD @ 550 nm
Mechanical & Environmental
- Outer Dimension Tolerance: +0 / −0.25 mm
- Clear Aperture: Nominal size − 4 mm
- Maximum Thickness: 4 mm
- Operating Temperature: −60 °C to +80 °C
Materials & Finish
- Substrates: Optical glass or UV-grade fused silica (quartz)
- Surface Quality: 80/50 scratch-dig (MIL-O-13830A)
- Coatings: Vacuum-deposited metallic alloy (reflective ND only)
Construction Options
- Exposed front-surface metallic coating
- Protected laminated metallic coating
- Absorptive neutral density glass
Standard Products
| Description | Transmission (%) | Ø25 mm Item # | 50×50 mm Item # |
|---|---|---|---|
| ND 1% | 1 | XND0001 | ZND0001 |
| ND 3% | 3 | XND0003 | ZND0003 |
| ND 6% | 6 | XND0006 | ZND0006 |
| ND 12% | 12 | XND0012 | ZND0012 |
| ND 25% | 25 | XND0025 | ZND0025 |
| ND 50% | 50 | XND0050 | ZND0050 |
Customization Options
Custom ND filters are available from prototype to high-volume production, including:
- Non-standard sizes and shapes
- Specific OD values and wavelength bands
- Protected coatings for harsh or high-power environments
Contact us to discuss your application requirements or request a quotation.